Search for Gamma-Ray Spectral Lines from Dark Matter Annihilation up to 100 TeV toward the Galactic Center with MAGIC

Linelike features in TeV $\gamma$ rays constitute a “smoking gun” for TeV-scale particle dark matter and new physics. Probing the Galactic Center region with ground-based Cherenkov telescopes enables the search for TeV spectral features in immediate association with a dense dark matter reservoir at a sensitivity out of reach for satellite $\gamma$-ray detectors, and direct detection and collider experiments. We report on 223 hours of observations of the Galactic Center region with the MAGIC stereoscopic telescope system reaching $\gamma$-ray energies up to 100 TeV. We improved the sensitivity to spectral lines at high energies using large-zenith-angle observations and a novel background modeling method within a maximum-likelihood analysis in the energy domain. No linelike spectral feature is found in our analysis. Therefore, we constrain the cross section for dark matter annihilation into two photons to $⟨\sigma v⟩\lesssim 5\times {10}^{-28}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ at 1 TeV and $⟨\sigma v⟩\lesssim 1\times {10}^{-25}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ at 100 TeV, achieving the best limits to date for a dark matter mass above 20 TeV and a cuspy dark matter profile at the Galactic Center. Finally, we use the derived limits for both cuspy and cored dark matter profiles to constrain supersymmetric wino models.

Figure 1

95% CL upper limits on the annihilation cross section $⟨\sigma v⟩$ into two $\gamma$ rays assuming the Einasto profile, as a function of energy. Observed limits (black dots) are shown together with the mean expected limits (black dotted line) and the 68% (green) and 95% (yellow) containment bands.

Figure 2

95% CL upper limits to $\gamma$-ray spectral lines from DM annihilation for the Einasto (red solid line) and cored Zhao (yellow dashed line, [56]) profiles, in comparison to previous works by MAGIC (long gray dashed line, [71]), Fermi-LAT (black and gray dash-dotted lines, [28]), H.E.S.S. (black dotted line, [32]), HAWC (gray dash-dotted-dotted line, [70]), and DAMPE (short gray dashed line, [73]). dSphs: dwarf spheroidal galaxies.

Figure 3

Upper limits for the four DM density profiles considered in this Letter: the cuspy Einasto Galactic density profile (red solid line), the NFW profile (cyan dashed line), a DM core according to Ref. [56] (yellow dashed line), and the Burkert fit from Ref. [53] (green dotted line), compared against the total $⟨\sigma v⟩$ corresponding to annihilation of two SUSY winos [i.e., ${\mathrm{SU}(2)}_L$ triplets] into a $\gamma \gamma$ pair according to Refs. [11, 13, 14, 15] (gray solid line; see text for details). The vertical blue hatched region indicates wino masses from 2.7 to 3.0 TeV which are consistent with the observed DM relic density [14].